Computer systems can provide user environment management and/or policy control for computing devices (e.g., Windows based PCs). A system policy can be defined within an enterprise computer network either: to respond to system events such as computer startup/shutdown, user login/logoff, process start/stop, and session changes, etc.; or to prevent or control user behavior in applications and the desktop environment. For example, a pre-defined script can run when a user logs in to a corporate network; a particular group of users can be prevented from using parts of an application. The conventional user environment and/or policy control mechanisms, however, are limited to handle application and system level events and policies, not events and policies related to web browsers. Some example of web events include webpage loading, URL clicking, adding/deleting a tab within a web browser, etc. Typical policies include, for example, blocking of URLs and redirection and preventing use of particular buttons or menus inside an web page.